Issue #2811841 by hchonov, tstoeckler, Berdir: Add test coverage ensuring user...

Issue #2811841 by hchonov, tstoeckler, Berdir: Add test coverage ensuring user input is mapped on the correct form elements when elements are reordered

core/modules/system/tests/modules/entity_test/src/Plugin/Field/FieldWidget/ShapeOnlyColorEditableWidget.php

+<?php
+
+namespace Drupal\entity_test\Plugin\Field\FieldWidget;
+
+use Drupal\Core\Field\FieldItemListInterface;
+use Drupal\Core\Field\WidgetBase;
+use Drupal\Core\Form\FormStateInterface;
+
+/**
+ * Plugin implementation of the 'shape_only_color_editable_widget' widget.
+ *
+ * @FieldWidget(
+ *   id = "shape_only_color_editable_widget",
+ *   label = @Translation("Shape widget with only color editable property"),
+ *   field_types = {
+ *     "shape"
+ *   },
+ * )
+ */
+class ShapeOnlyColorEditableWidget extends WidgetBase  {
+
+  /**
+   * {@inheritdoc}
+   */
+  public function formElement(FieldItemListInterface $items, $delta, array $element, array &$form, FormStateInterface $form_state) {
+    $element['shape'] = [
+      '#type' => 'hidden',
+      '#value' => $items[$delta]->shape
+    ];
+
+    $element['color'] = [
+      '#type' => 'textfield',
+      '#default_value' => isset($items[$delta]->color) ? $items[$delta]->color : NULL,
+      '#size' => 255,
+    ];
+
+    return $element;
+  }
+
+}

core/tests/Drupal/FunctionalTests/Entity/ContentEntityFormCorrectUserInputMappingOnFieldDeltaElementsTest.php

+<?php
+
+namespace Drupal\FunctionalTests\Entity;
+
+use Drupal\Core\Entity\ContentEntityInterface;
+use Drupal\Core\Entity\ContentEntityStorageInterface;
+use Drupal\Core\Field\FieldStorageDefinitionInterface;
+use Drupal\field\Entity\FieldConfig;
+use Drupal\field\Entity\FieldStorageConfig;
+use Drupal\Tests\BrowserTestBase;
+
+/**
+ * Tests the correct mapping of user input on the correct field delta elements.
+ *
+ * @group Entity
+ */
+class ContentEntityFormCorrectUserInputMappingOnFieldDeltaElementsTest extends BrowserTestBase  {
+
+  /**
+   * The ID of the type of the entity under test.
+   *
+   * @var string
+   */
+  protected $entityTypeId;
+
+  /**
+   * The field name with multiple properties being test with the entity type.
+   *
+   * @var string
+   */
+  protected $fieldName;
+
+  /**
+   * {@inheritdoc}
+   */
+  public static $modules = ['entity_test'];
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function setUp() {
+    parent::setUp();
+    $web_user = $this->drupalCreateUser(['administer entity_test content']);
+    $this->drupalLogin($web_user);
+
+    // Create a field of field type "shape" with unlimited cardinality on the
+    // entity type "entity_test".
+    $this->entityTypeId = 'entity_test';
+    $this->fieldName = 'shape';
+
+    FieldStorageConfig::create([
+      'field_name' => $this->fieldName,
+      'entity_type' => $this->entityTypeId,
+      'type' => 'shape',
+      'cardinality' => FieldStorageDefinitionInterface::CARDINALITY_UNLIMITED,
+    ])
+      ->save();
+    FieldConfig::create([
+      'entity_type' => $this->entityTypeId,
+      'field_name' => $this->fieldName,
+      'bundle' => $this->entityTypeId,
+      'label' => 'Shape',
+      'translatable' => FALSE,
+    ])
+      ->save();
+
+    entity_get_form_display($this->entityTypeId, $this->entityTypeId, 'default')
+      ->setComponent($this->fieldName, ['type' => 'shape_only_color_editable_widget'])
+      ->save();
+  }
+
+  /**
+   * Tests the correct user input mapping on complex fields.
+   */
+  public function testCorrectUserInputMappingOnComplexFields() {
+    /** @var ContentEntityStorageInterface $storage */
+    $storage = $this->container->get('entity_type.manager')->getStorage($this->entityTypeId);
+
+    /** @var ContentEntityInterface $entity */
+    $entity = $storage->create([$this->fieldName => [
+      ['shape' => 'rectangle', 'color' => 'green'],
+      ['shape' => 'circle', 'color' => 'blue'],
+    ]]);
+    $entity->save();
+
+    $this->drupalGet($this->entityTypeId . '/manage/' . $entity->id() . '/edit');
+
+    // Rearrange the field items.
+    $edit = array(
+      "$this->fieldName[0][_weight]" => 0,
+      "$this->fieldName[1][_weight]" => -1,
+    );
+    // Executing an ajax call is important before saving as it will trigger
+    // form state caching and so if for any reasons the form is rebuilt with
+    // the entity built based on the user submitted values with already
+    // reordered field items then the correct mapping will break after the form
+    // builder maps over the new form the user submitted values based on the
+    // previous delta ordering.
+    //
+    // This is how currently the form building process works and this test
+    // ensures the correct behavior no matter what changes would be made to the
+    // form builder or the content entity forms.
+    $this->drupalPostForm(NULL, $edit, t('Add another item'));
+    $this->drupalPostForm(NULL, [], t('Save'));
+
+    // Reload the entity.
+    $entity = $storage->load($entity->id());
+
+    // Assert that after rearranging the field items the user input will be
+    // mapped on the correct delta field items.
+    $this->assertEquals($entity->get($this->fieldName)->getValue(), [
+      ['shape' => 'circle', 'color' => 'blue'],
+      ['shape' => 'rectangle', 'color' => 'green'],
+    ]);
+  }
+
+}